The invention relates to an air vent valve in which a cut valve and a check valve are integrally formed. The cut valve normally discharges vapor in a fuel tank to a canister, and is closed to prevent fuel from leaking outside when a vehicle is turned or inclined. The check valve is provided between the cut valve and a canister to open and close for maintaining an internal pressure of the fuel tank in a predetermined range according to a pressure change in the fuel tank. The present invention also relates to an air vent mechanism of the fuel tank using the air vent valve.
Conventionally, a fuel tank of a vehicle has been provided with a cut valve for releasing an internal pressure of the tank by discharging vapor (fuel vapor) generated from fuel (gasoline) to outside the tank, and for preventing the fuel from leaking by closing the valve when the fuel liquid surface is elevated. The vapor discharged to outside the tank through the cut valve is released in the atmosphere after a hydrocarbon component is removed through a canister. Generally, a two-way valve called xe2x80x9ccheck valvexe2x80x9d is disposed between the canister and the cut valve, and is opened or closed according to the pressure change in the fuel tank to thereby maintain the internal pressure of the fuel tank in a predetermined range.
A conventional air vent mechanism of the fuel tank using the cut valve and check valve is structured as shown in FIG. 6. More specifically, cut valves a are provided at positions (two positions on both sides of the tank in the drawing) on an upper wall of a fuel tank t. A pipe b is attached to each cut valve a, and is extended to form a single system air vent pipe c. The air vent pipe c is connected to the canister for guiding the vapor from the fuel tank t to the canister through the cut valves a, the pipes b and the air vent pipe c. The vapor is discharged to the atmosphere while the hydrocarbon component is removed at the canister.
In this case, the cut valves a normally discharge the vapor in the fuel tank t to outside the tank. At the same time, the cut valves a detect the fuel liquid surface, and are closed when the fuel liquid surface in the tank t is elevated, thereby preventing the fuel from leaking outside the tank t.
Also, normally, a check valve d is disposed between the cut valves a and the canister (in FIG. 6, the check valve d is located at a base end of the air vent pipe c). When the inner pressure of the fuel tank t becomes higher or lower than the predetermined levels, the check valve d is opened and releases the pressure (positive pressure or negative pressure) in the fuel tank t together with discharging the vapor.
As shown in FIG. 6, the cut valves a are provided at several positions (in the drawing, two positions) of the fuel tank t. Accordingly, when the vehicle is turned or inclined, since the fuel in the fuel tank t is one-sided, one of the cut valves a is immersed in the fuel and closed. Thus, the vapor in the fuel tank t is discharged through the other cut valve a to release the internal pressure of the tank. Incidentally, according to a shape of the fuel tank t, the cut valves may be provided at more than three positions.
However, in the conventional air vent mechanism described above, it is necessary to provide a plurality of the pipes b for connecting the cut valves a provided at the plural positions of the fuel tank t to the air vent pipe c. Also, it is necessary to provide a connector having three or four branches for fitting the pipes b to the air vent pipe c, thereby increasing the number of components constituting the air vent mechanism. Further, a large number of steps are required for assembling the pipings, connecting the respective pipings and the air vent pipe through the connectors, and installing the check valve, thereby increasing a cost.
Further, depending on a type of a car, a lay-out of the piping may be limited to minimize a space. In such a case, it may be difficult to constitute the air vent mechanism having the plural pipes b.
In view of the above problems, the present invention has been made, and an object of the invention is to provide an air vent mechanism wherein the air vent operation is reliably carried out with a simple piping, so that the mechanism can be assembled with few components and less assembly labor at a lower cost.
Further objects and advantages of the invention will be apparent from the following description of the invention.
In order to attain the above object, the present invention provides a composite type air vent valve, wherein a cut valve and a check valve are integrally combined. The cut valve normally discharges vapor in a fuel tank to outside the tank and sends the vapor to a canister. When a vehicle is turned or inclined, the valve is closed to prevent the fuel from leaking out. The check valve is disposed between the cut valve and the canister, and is opened or closed according to a pressure change in the fuel tank to maintain an inner pressure of the fuel tank in a predetermined range.
The air vent valve includes a check valve portion having a tank side port and an atmosphere side port for opening and closing between the ports as needed according to a pressure change in the fuel tank; a cut valve portion having a tank side port and an atmosphere side port so that normally the vapor in the fuel tank is discharged from the atmosphere side port to outside the tank through the tank side port in a state that both ports are communicated, and when the vehicle is turned or inclined and the fuel liquid surface is elevated, the fuel liquid surface is detected to close between the ports; an atmosphere side connecting portion communicating with the atmosphere side port of the check valve portion and connected to the canister; a communicating path for communicating the tank side port of the check valve portion with the atmosphere side port of the cut valve portion; and a tank side connecting portion for communicating with the communicating path and connected to other cut valve. The cut valve portion is attached to an upper wall of the fuel tank to cover an attaching hole in a state where the cut valve portion is projected into the fuel tank through the attaching hole.
Also, in the present invention, a plurality of cut valves is provided on an upper wall of the fuel tank and is connected to the canister for discharging the vapor in the fuel tank to outside thereof in a normal state. When the vehicle is turned or inclined, the cut valves detect a fuel liquid surface and are closed to prevent the fuel from leaking. A check valve is disposed between the cut valve and the canister to be closed or opened according to a pressure change in the fuel tank. When the fuel tank is in a pressurized state, the check valve is opened to release the vapor in the fuel tank into the atmosphere through the cut valve, the check valve and the canister in this order. When the fuel tank is in a reduced pressure state, the check valve is opened to communicate the atmosphere with the fuel tank to release the reduced pressure state. Further, the composite type air vent valve of the present invention described above is attached on the upper wall of the fuel tank as one of the cut valves and the check valve. Other cut valves are connected to the tank side connecting portion of the composite type air vent valve, and the canister is connected to the atmosphere side connecting portion.
According to the present invention, as described above, the composite type air vent valve includes the check valve portion integrally combined with the cut valve portion. The check valve portion controls the inner pressure of the fuel tank. The cut valve portion discharges the vapor in the fuel tank to outside thereof, and, at the same time, prevents the fuel from leaking. The check valve portion and the cut valve portion are connected to each other through the communicating path. The tank side connecting portion is communicated with the communicating path, and the atmosphere side connecting portion is communicated with the atmosphere side port of the check valve portion.
As in the air vent mechanism according to the present invention described above, the composite type air vent valve is attached to a predetermined position on the upper wall of the fuel tank in a state where the cut valve portion is projected into the tank as one of the cut valves and the check valve. One or more other cut valves are attached to the fuel tank and are connected to the tank side connecting portion. The atmosphere side connecting portion is connected to the canister, thereby constituting the fuel tank air vent mechanism.
Next, an operation of the air vent mechanism using the composite type air vent valve according to the present invention will be explained.
Normally, the vapor in the fuel tank is introduced into the communicating path through the cut valve portion due to the pressure increase in the fuel tank. At the same time, the vapor from the other cut valve is also introduced into the communicating path from the tank side connecting portion through the piping. The vapor flows to the atmosphere side connecting portion through the check valve portion opened by the pressure from the tank side, and is discharged into the atmosphere through the canister connected to the atmosphere side connecting portion.
Also, in the case that the fuel in the fuel tank is one-sided when the vehicle is turned or inclined, and the cut valve portion of the composite type air vent valve is immersed in the fuel, the cut valve portion detects the fuel liquid surface and closes, thereby preventing the fuel from leaking outside the tank through the cut valve portion. At this time, the vapor discharged to outside the tank from the other cut valve in an open state is introduced into the communicating path of the composite type air vent valve of the invention from the tank side connecting portion through the piping. Further, the vapor is introduced into the canister from the atmosphere side connecting portion through the check valve portion to thereby be discharged into the atmosphere. On the other hand, in the case that the vehicle is turned or inclined, the fuel in the fuel tank is one-sided to the other direction. The other cut valve is immersed into the fuel to be closed. In that case, the vapor is released into the atmosphere, in the same manner as described above, through the cut valve portion of the composite type air vent valve of the invention in the opened valve state.
Further, the check valve portion of the composite type air vent valve is normally in the closed state. However, the pressure in the fuel tank may exceed a predetermined pressure due to a large quantity of the vapor, the solar heat, vibration of the fuel tank during driving, or elevation of the fuel liquid surface through fueling. In that case, the check valve portion is opened due to the pressure so that the vapor is discharged into the atmosphere as described above. At the same time, the pressurized state in the fuel tank is released. Also, in the case that the inner pressure of the fuel tank becomes a reduced pressure state below a predetermined pressure due to cooling-down or rapid reduction of the fuel, the check valve portion is opened by the atmospheric pressure. Thus, the interior of the fuel tank is communicated with the atmosphere through the same path as described above, thereby releasing the reduced pressure condition.
Accordingly, similar to the case of the vapor discharging, even when the fuel in the tank is one-sided due to turning or inclination of the vehicle, the pressure in the tank can be securely controlled by either of the cut valve of the composite type air vent valve or the other cut valve in the opened state, thereby maintaining the inner pressure of the fuel tank at a predetermined level.
As described above, according to the invention, the composite type air vent valve has the check valve portion and the cut valve portion integrated together. The composite type air vent valve can be used as one of the cut valves, and the other cut valve is connected to the tank side connection portion. Also, the atmosphere side connecting portion is connected to the canister, thereby constituting the air vent mechanism. Therefore, it is not necessary to provide a separate-check valve, thereby reducing the number of the pipes and providing the highly reliable air vent mechanism with the simple piping and layout. The number of the components and assembly steps are reduced, thereby reducing the cost.
Therefore, according to the present invention, the composite air vent valve and air vent mechanism constitute the highly reliable air vent mechanism with less number of the components and assembly steps in a simple way at a lower cost.